1. Field of the Invention
The present invention relates to display devices and particularly to a display device having a high-precision screen.
2. Description of the Related Art
A liquid crystal display (LCD), a type of display device, comprises a TFT (thin film transistor) substrate, a counter substrate, and a liquid crystal layer sandwiched between the two substrates. On the TFT substrate, pixels are formed in the form of a matrix, and the pixels each include a pixel electrode and a TFT. Images are produced by controlling the transmittance rate of light passing through the liquid crystal molecules on a pixel-by-pixel basis. Since LCDs are flat and lightweight, the range of their application is getting wider in various fields. For instance, small-sized LCDs are widely used in cell phones, DSCs (digital still camera), and so on.
In small- and middle-sized LCDs, top-gate TFTs and poly-Si semiconductor layers are often used. This is because Poly-Si is larger in mobility than a-Si and a drive circuit can be formed on the TFT substrate. JP-2000-275676-A discloses a LCD using such TFTs. JP-2000-275676-A teaches that it is effective to use double-gate TFTs to reduce leakage current.